An electronic paper as an image display that utilizes a technique of an electrophotoretic method, a particle migration method, or the like has been proposed as an alternative to a liquid crystal display (LCD). In the electronic paper, the migration of particles using the static electricity enables a repetitive display and deletion of an image. The electronic paper has advantages that it realizes a view at wider angles such as an angle close to that of typical printed matters in comparison with the LCD, requires smaller power consumption, and has a memory function. Therefore, the electronic paper draws attention as a low-priced next-generation display (see, for example, Patent Documents 1 to 3).
FIG. 9 shows a basic configuration of the conventional electronic paper 1000. The electronic paper 1000 shown in FIG. 9 includes a pair of opposing substrates (110, 120) wherein at least one of them is a transparent substrate, and partitions 130 which maintain a distance between both substrates (110, 120). Both substrates (110, 120) and the partitions 130 form a cell structure and each space of the cell structure encloses particles having different colors (140A, 140B). A selected distance between the substrate 110 and the substrate 120 is a distance between which particles can migrate and a contrast can be maintained.
More specifically, as shown in FIG. 10, the conventional electronic paper 2000 includes a lower substrate 210, an upper substrate 220, and a partition layer 230 lying between both substrates (210, 220).
The lower substrate 210 includes lower electrodes 214 formed on a surface of a lower sheet member 212 and an insulating layer 216 formed on a surface of a lower sheet member 212 so as to cover the lower electrodes 214. On the other hand, the upper substrate 220 includes an upper electrode 224 formed on a surface of an upper sheet member 222 and an insulating layer 226 formed on the upper sheet member 222 so as to cover the upper electrode 224. The partition layer 230 includes a plurality of partitions 232. Each space between the neighboring partitions 232 is formed into a cell space 250 in which powder particles 240 (240A or 240B) are enclosed.
The partitions 232 of the partition layer 230 serve to keep a gap between the lower substrate 210 and the upper substrate 220. The partitions 232 are formed so as to extend vertically upwardly from the insulating layer 216 covering the lower electrodes 214. A bonding layer 234 is formed on an upper surface of each partition 232. Each partition 232 is connected to the upper substrate 220 through the bonding layer 234.
When voltage (260) is applied to the lower electrodes 214 and the upper electrode 224 in the electronic paper 2000, the powder particles 240 within the cell spaces 250 migrate, thereby displaying an image on the electronic paper 2000. In an example shown in FIG. 10, the positively-charged powder particles 240A migrate toward the lower electrodes 214, whereas the negatively-charged powder particles 240B migrate toward the upper electrode 224.
The electronic paper 2000 is produced in a manner as described below.
Initially, as shown in FIG. 11(a), a substrate structure in which the lower electrodes 214 are formed on the surface of the lower sheet member 212 is prepared. Subsequently, as shown in FIG. 11(b), the insulating layer 216 is formed on the surface of the sheet member 212 so as to cover the electrodes 214. Then, as shown in FIG. 11(c), the partitions 232 are formed on the insulating layer 216.
As shown in FIG. 11(d), after the powder particles 240 (240A, 240B) are filled in each space between the partitions 232, the bonding layer 234 is formed on the surface of each partition 232. Subsequently, as shown in FIG. 11(e), the substrate structure (i.e., upper substrate) including the upper sheet member 222, the upper electrode 224, and the insulating layer 226 is bonded to the bonding layer 234 on each partition 232, thereby obtaining the electronic paper 2000.